Linerless labels, such as shown in U.S. Pat. Nos. 3,051,588, 3,285,771, and 4,851,383, and in Canadian patent 1,248,412, are known to have advantages over conventional pressure sensitive labels which are mounted on a liner which has been coated with a release coating. In the conventional labels the liner acts as a support for transport, printing and storage, and after the label is removed from the liner it must be disposed of. A linerless label, on the other hand has the face coated with a release coating, and the back with a pressure sensitive adhesive (PSA), and is wound in a roll configuration so that the PSA is in contact with the release coating, and the release coating faces outwardly. The linerless construction offers advantages and lower costs due to substantial material reduction, elimination of disposal concerns and costs associated with release coated liners, and in providing approximately twice as many labels per roll.
While linerless labels have numerous advantages, they have not had widespread commercial acceptance, perhaps due in part to impediments to easy and clean peeling off of the PSA from the release coating in the roll format. If the adhesion of the PSA to the substrate is not strong enough (and this adhesion can degrade over time under some environmental conditions and materials), adhesive may stick to the release coating, or the substrate may be torn.
According to the present invention, a linerless label stock, and a method of making linerless labels, are provided which enhance the viability of linerless labels by providing a more secure adhesion of the PSA to the substrate than is typically provided in the prior art. According to the present invention a tie coat is provided which facilitates adherence of the PSA to a first face (the "back") of the substrate, the tie coat adhering to both the substrate first face and the PSA. The tie coat preferably comprises a dispersion of a pigment, such as silica, with a binder, such as PVA. For example, the tie coat may consist essentially of about 30-40 parts silica dispersion, about 20-35 parts PVA, and about 30-40 water. Printing may be provided on the substrate first face, or may be applied onto the release coating by certain techniques.
According to the method of making linerless labels of the invention, a coating machine is utilized with a substrate having first and second faces. The method comprises the steps of: (a) Continuously moving the substrate in a first direction through the coating machine, and substantially sequentially: (b) With the coating machine, applying in a predetermined sequence to the moving substrate a tie coating to the substrate first face, a release coating to the substrate second face, and a pressure sensitive adhesive to the tie coating. (c) Cutting the substrate to form individual labels. And, (d) rolling the substrate into a roll, with the release coated second face on the outside of the roll.
In the practice of the method set forth above, the predetermined sequence of step (b) is preferably to apply the tie coating first, then the release coating, and then the pressure sensitive adhesive. The cutting step may be die cutting, and drying at a rate much faster than ambient air drying may be practiced before steps (c) and (d), by hot air, infrared, or like drying technique.
It is the primary object of the present invention to provide an advantageous linerless label stock, and a simple yet effective method for making the stock. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.